Substantial progress has been made in examining the mechanism of action and the effects of amphetamine as well as amphetamine analogs. We have found that 3H-amphetamine is sequestered by synaptosomal fractions from brain. The neurotoxic effects of MDMA on brain serotonin neurons has been explored further by both biochemical techniques as well as autoradiographical techniques. Overall, these studies elucidate the mechanism of action of amphetamine as well as further explain the neurotoxic effects of drugs like MDMA.